Abstract

An isocratic RP‐HPLC method for the separation and identification of selected flavonoids (quercetin, rutin, luteolin‐7‐O‐glucoside, kaempferol and kaempferol‐3‐O‐glucoside) in commercial berry juices (blackcurrant, blueberry, red raspberry and cherry) was developed with the aid of central composite design and response surface methodology. The optimal separation conditions were a mobile phase of 85:15 (% v/v) water–acetonitrile, pH 2.8 (adjusted with formic acid), flow rate 0.5 mL min−1 and column temperature 35°C. The obtained levels of bioflavonoids (mg per 100 mL of juice) were as follows: for quercetin, ca. 0.21–5.12; for kaempferol, ca. 0.05–1.2; for rutin, ca. 0.4–6.5; for luteolin‐7‐O‐glucoside, ca. 5.6–10.2; and for kaempferol‐3‐O‐glucoside, ca. 0.02–0.12. These are considerably lower than the values in fresh fruits. Total phenolic, flavonoid and anthocyanin contents were determined spectrophotometrically. Total flavonoid content varied as follows: blackcurrant > blueberry > red raspberry > cherry. The antioxidant activity of juice extracts (DPPH and ABTS methods) expressed as IC50 values varied from 8.56 to 14.05 mg L−1. These values are ~2.5–3 times lower than quercetin, ascorbic acid and Trolox®, but compared with rutin and butylhydroxytoluene, berries show similar or better antioxidant activity by both the DPPH and ABTS methods.

The hydrophilic and lipophilic contribution to total antioxidant activity

Arnao, M. B.; Cano, A.; Acosta, M.

Standardisation of an extract of propolis and identification of the major compounds

Arvouet‐Grand, A.; Vennat, B.; Pourrat, A.; Legret, P.

A quantitative determination of flavonoids by column high‐performance liquid chromatography with mass spectrometry and ultraviolet absorption detection in Artemisia afra and comparative studies with various species of Artemisia plants